Medium- and Low-Temperature Integrated Refrigerating/Freezing System

ABSTRACT

A medium- and low-temperature integrated refrigerating/freezing system ( 40 ) comprises an integrated unit ( 41 ), a medium-temperature refrigerating cabinet ( 43 ), a low-temperature freezing cabinet ( 42 ) and corresponding connecting pipes ( 44 ). The integrated unit ( 41 ) further comprises a common condenser ( 54 ) for condensing the high-temperature and high-pressure gaseous refrigerant in the medium-temperature refrigerating system and the low-temperature freezing system, a common reservoir ( 55 ) for the storage of the high-temperature and high-pressure liquid refrigerant in the medium-temperature refrigerating system and the low-temperature freezing system, a subcooling adjusting mechanism ( 56, 57 ) for adjusting the subcooling degree in the low-temperature freezing system and a suction temperature adjusting mechanism ( 431, 432, 58 ) for adjusting the suction temperature of the low-temperature freezing system.

BACKGROUND

The present disclosure relates to a medium- and low-temperatureintegrated refrigerating/freezing system, and in particular to anintegrated system for providing medium-temperature refrigerating andlow-temperature freezing for foods and cold drinks, etc. in supermarketsand convenience stores.

In real life, various freezing display cabinets are provided insupermarkets or convenience stores for providing a freezing environmentfor preservation and freezing of foods, beverage and cold drinks whenthe ambient temperature is relatively higher. Generally differentproducts have different requirements to the temperature of freezing andpreservation. Usually, freezing systems are classified aslow-temperature freezing systems and medium-temperature refrigerationsystems. Low-temperature freezing systems usually provide an evaporatortemperature of about 30-35 degrees centigrade below zero, mainly forproducts such as ice cream or other frozen food. Medium-temperaturerefrigerating systems usually provide an evaporator temperature of about8-10 degrees centigrade below zero for products such as milk, drinks,produce, meat, and other perishable foods. Currently, a low-temperaturefreezing system and a medium-temperature refrigerating system are twoindependent systems without mutual interference, because the compressionratios of the two systems are different, so are the energy efficienciesof these systems. FIG. 1 is a schematic diagram of the structure of amedium-temperature refrigerating system which comprises a compressor 1,a condenser 2, an expansion valve 4, a reservoir 3, an evaporator 5connected with a medium-temperature refrigerating cabinet andrefrigerant pipes 6 correspondingly connecting the devices and forming aclosed circulation loop. In operation, low-temperature and low-pressuregaseous refrigerant is changed into high-temperature and high-pressuregas after having been compressed by the compressor 1. After enteringinto the condenser 2, the high-temperature and high-pressure gaseousrefrigerant releases its heat to the ambient, transforms into ahigh-temperature and high-pressure liquid and flows into the expansionvalve 4 via the reservoir 3. The expansion valve 4 reduces the pressureof the refrigerant and adjusts the flow rate of the refrigerant, so asto enable the high-temperature and high-pressure liquid refrigerant tochange into low-temperature and low-pressure two-phase liquid and gasand to flow into the evaporator 5. A fan (not shown) is also providednear the evaporator inside the refrigerating cabinet for blowing airtowards the surface of the coiled pipes of the evaporator in order tohave heat exchange between the low-temperature and low-pressure liquidrefrigerant in the coiled pipes of the evaporator 5 and the air flowingthrough the surface of the coiled pipes of the evaporator, so as togenerate cold air for preservation and storage of various foods in therefrigerating cabinet. The refrigerant changes into a low-temperatureand low-pressure gas after absorbing heat and flows back to thecompressor 1, completing a complete and closed cycle by the refrigerant.

FIG. 2 is a schematic diagram of the structure of a low-temperaturefreezing system, of which the working principle is essentially the sameas that of the medium-temperature refrigerating system. Since thelow-temperature freezing system is required for generating relativelylower temperature, the system has a relatively high compression ratio,and in order to protect the low-temperature compressor it is needed tolower the exhaust temperature of the low-temperature compressor 1. Incomparison with a medium-temperature refrigerating system, therefore, inthe structure of the low-temperature freezing system, the refrigerantflowing out of the reservoir 3 flows into a branch as well as directlyinto the evaporator 5. In the branch, the high-temperature andhigh-pressure liquid refrigerant from the reservoir 3 flows via aninjection valve 7, expands, absorbs heat and changes into alow-temperature and low-pressure gas which is provided directly to thecompressor 1. The refrigerant in the branch lowers the suctiontemperature of the compressor 1, thereby the exhaust temperature of thecompressor 1 being lowered and the compressor 1 being effectivelyprotected.

The two currently available independent systems are capable of providingsupermarkets and convenience stores with a low-temperature freezingsystem and a medium-temperature refrigerating system respectively, andmeeting the requirements for the storage of various foods atmedium-temperature and low-temperature. However, since two independentsystems are employed in this case, machine rooms are needed in thesupermarkets and convenience stores for accommodating the compressorsand condensers of the two systems, which not only wastes space insupermarkets and convenience stores, but also adds complexity of siteinstallation. Meanwhile, the repetitive use of the condensers and thereservoirs by the two independent systems wastes raw materials andincreases the hardware costs of the systems, both being disadvantageousto energy saving and cost reduction.

SUMMARY

In one aspect, a medium- and low-temperature integratedrefrigerating/freezing system may provide medium temperaturerefrigeration for storing foods, etc. and low temperature freeze forstoring cold drinks, etc. The system may comprise an integrated unit, a(group of) medium-temperature refrigerating cabinet(s), a (group of)low-temperature freezing cabinet(s) and corresponding connecting pipes.The integrated unit may further comprise: a common condenser forcondensing high-temperature and high-pressure gaseous refrigerant in themedium-temperature refrigerating system and the low-temperature freezingsystem; a common reservoir for storing the high-temperature andhigh-pressure liquid refrigerant in the medium-temperature refrigeratingsystem and the low-temperature freezing system; a subcooling adjustingmechanism for adjusting the subcooling of the low-temperature freezingsystem; and a suction temperature adjusting mechanism for adjustingintake temperature of the low-temperature freezing system.

The system may have compact structure and energy saving as well as easyinstallation and relatively high energy utilization efficiency.

The system may provide a medium- and low-temperature integratedrefrigerating/freezing system, in which the integrated unit furthercomprises a (group of) medium-temperature compressor(s) and a (group of)low-temperature compressor(s).

The system may provide a medium- and low-temperature integratedrefrigerating/freezing system, in which the medium-temperaturerefrigerating cabinet and the low-temperature freezing cabinet compriserespectively an evaporator, an expansion valve and a product cabinet forfood placement.

The system may provide a medium- and low-temperature integratedrefrigerating/freezing system, in which the suction ends of the (groupof) medium-temperature compressor(s) and the (group of) low-temperaturecompressor(s) are respectively connected to the evaporators of themedium-temperature refrigerating cabinet and the low-temperaturefreezing cabinet, and the exhaust ends thereof are jointly connected tothe inlet end of the common condenser.

The system may provide a medium- and low-temperature integratedrefrigerating/freezing system, in which the outlet end of the commoncondenser is connected to the inlet end of the reservoir.

The system may provide a medium- and low-temperature integratedrefrigerating/freezing system, in which the expansion valve in theintegrated unit, an intermediate heat exchanger and the correspondingconnecting pipes form the subcooling adjusting mechanism.

The system may provide a medium- and low-temperature integratedrefrigerating/freezing system, in which a first inlet end of theintermediate heat exchanger of the subcooling adjusting mechanism isdirectly connected to the reservoir, and a second inlet end of theintermediate heat exchanger of the subcooling adjusting mechanism isconnected to the reservoir via the expansion valve.

The system may provide a medium- and low-temperature integratedrefrigerating/freezing system, in which a first outlet end of theintermediate heat exchanger is connected to the inlet end of thelow-temperature freezing cabinet.

The system may provide a medium- and low-temperature integratedrefrigerating/freezing system, in which the suction temperatureadjusting mechanism comprises a first branch connecting the secondoutlet end of the intermediate heat exchanger with the suction end ofthe medium-temperature compressor, and a second branch connecting thesecond outlet end of the intermediate heat exchanger with the suctionend of the low-temperature compressor, wherein the second branchcontains an adjustment valve.

The system may provide a medium- and low-temperature integratedrefrigerating/freezing system, in which the integrated unit is connectedto the medium-temperature refrigerating cabinet and the low-temperaturefreezing cabinet in a plug-and-play manner

In another aspect, a refrigerating system comprises: at least onemedium-temperature refrigerating device comprising at least onemedium-temperature evaporator; at least one low-temperature freezingdevice comprising at least one low-temperature evaporator; an integratedunit comprising: at least one medium-temperature compressor connected tothe medium-temperature evaporator; at least one low-temperaturecompressor connected to the low-temperature evaporator; a condenserconnected to the exhaust ends of the at least one medium-temperaturecompressor and the at least one low-temperature compressor forcondensing the high-temperature and high-pressure gaseous refrigerantexhausted from the exhaust ends of the at least one medium-temperaturecompressor and the at least one low-temperature compressor; a reservoirconnected to the condenser for storing the high-temperature andhigh-pressure liquid refrigerant exhausted from the condenser; asubcooling adjusting mechanism connected with the reservoir and to thelow-temperature evaporator for adjusting the subcooling of thelow-temperature freezing circulation system; a suction temperatureadjusting mechanism connected with the reservoir and respectively to thelow-temperature compressor and the medium-temperature compressor foradjusting the suction temperature of the low-temperature freezingcirculation system; and a medium-temperature connecting pipelineconnected to the reservoir and the medium-temperature evaporator.

The system may provide a refrigerating system, in which the subcoolingadjusting mechanism comprises an intermediate heat exchanger connectedto the low-temperature evaporator, a first inlet end of the intermediateheat exchanger is directly connected to the reservoir, and a secondinlet end thereof is connected to the reservoir via an expansion valve.

The system may provide a refrigerating system, in which the first outletend of the intermediate heat exchanger is connected to thelow-temperature evaporator of the low-temperature freezing device.

The system may provide a refrigerating system, in which the suctiontemperature adjusting mechanism comprises a first branch connecting thesecond outlet end of the intermediate heat exchanger with the suctionend of the medium-temperature compressor, and a second branch connectingthe second outlet end of the intermediate heat exchanger with thesuction end of the low-temperature compressor, wherein the second branchcontains an adjustment valve.

The system may be implemented to effectively reduce installation spacefor the freezing system. A plug-and-play connection may be employed tofacilitate the system's site installation and later adjustments andmaintenance. The integrated design may optimize the layout of thepipelines. The whole system may offer simplified hardware structure andhigh performance

The details of one or more embodiments are set forth in the accompanyingdrawings and the description below. Other features, objects, andadvantages will be apparent from the description and drawings, and fromthe claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of the structure of a prior artmedium-temperature refrigerating system.

FIG. 2 is a schematic diagram of the structure of a prior artlow-temperature freezing system.

FIG. 3 is a schematic diagram of the structure of an embodiment of thepresent medium- and low-temperature integrated refrigerating/freezingsystem.

FIG. 4 is a schematic diagram of the structure of the medium- andlow-temperature refrigerating/freezing cabinet of the system of FIG. 3.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

It is easily understood that according to the technical solutions of thepresent disclosure, those skilled in the art would be able to proposeother embodiments of the medium- and low-temperature integratedrefrigerating/freezing system of the present invention without departingfrom the real spirit of the present invention; therefore, the followingembodiments and drawings are merely illustrative examples of thetechnical solutions of the present disclosure and they are not to bedeemed as the whole of the present disclosure or be deemed as limitingor defining the technical solutions of the present disclosure.

In FIG. 3, an embodiment of a medium- and low-temperature integratedrefrigerating/freezing system 40 mainly comprises an integrated unit 41,a low-temperature freezing cabinet 42, a medium-temperaturerefrigerating cabinet 43 and connecting pipes 44. The integrated unit 41has two inlet ends (inlets) 102, 104 and two outlet ends (outlets) 101,103. The housing of the low-temperature freezing cabinet 42 is providedwith an inlet end and an outlet end. The housing of themedium-temperature refrigerating cabinet 43 is provided with an inletend and an outlet end.

The integrated unit 41 comprises a housing 51, a low-temperaturecompressor 52, a medium-temperature compressor 53, a heat rejection heatexchanger (condenser) 54, a reservoir 55, an intermediate heat exchanger56, an expansion device (e.g., valve) 17, an adjustment valve 58, andthe associated connecting pipes 44. The housing 51 of the integratedunit 41 can be a sealed box, and it can also have doors or other similarstructures for installing/removing/accessing the low-temperaturecompressor 52, the medium-temperature compressor 53, the condenser 54,the reservoir 55, the intermediate heat exchanger 56 and the associatedconnecting pipes 44. The housing 51 may have shock absorption feet (notshown), and the housing 51 can be designed into a shock-proof andnoise-proof structure for improving system performance of the integratedunit 41 and for increasing system stability. Inside the housing 51, eachof the elements may be arranged for convenient connection between theelements and for laying out the connecting pipes 44. The integrated unitmay be a roof-mounted or other remote unit. Although shown connected toa single medium temperature evaporator and cabinet and a single lowtemperature evaporator and cabinet, a given integrated unit may beconnected to multiple such medium temperature evaporators and/orcabinets and/or multiple low temperature evaporators and/or cabinets.Also, each integrated unit may have multiple such medium temperaturecompressors and/or low temperature compressors in respective compressorsets.

The low-temperature freezing cabinet 42 may be similar to themedium-temperature refrigerating cabinet 43. Each cabinet 42, 43 (FIG.4) comprises a product cabinet 61 and a refrigerating device area 62.The product cabinet 61 can be designed into a structure suitable forstorage of foods and convenient for people to access, such as an openstructure or a compartment structure having one or more doors 65. Therefrigerating device area 62 is used for providing refrigerating air tothe product cabinet 61. The refrigerating device area 62 includes anexpansion device (e.g., valve) 63, heat absorption heat exchanger (e.g.,evaporator) 64 and associated connecting pipes 44. A fan (not shown) mayalso be provided to drive an airflow across the evaporator 64 andthrough the product cabinet 61. The cabinets may be rooms of a buildingor separate display or storage cases.

The connection of the whole medium- and low-temperature integratedrefrigerating/freezing system 40 is shown in FIG. 3, in which the outletend 101 of the integrated unit 41 is connected to the inlet end of thelow-temperature freezing cabinet 42 via the associated connecting pipes44, the outlet end of the low-temperature freezing cabinet 42 isconnected to the inlet end 102 of the of the integrated unit 41 via theconnecting pipes 44. The outlet end 103 of the integrated unit 41 isconnected to the inlet end of the medium-temperature refrigeratingcabinet 43 via the associated connecting pipes 44, and the outlet end ofthe medium-temperature refrigerating cabinet 43 is connected to theinlet end 104 of the of the integrated unit 41 via the associatedconnecting pipes 44. The integrated unit 41 may be connected in aplug-and-play manner to the medium-temperature refrigerating cabinet 43and the low-temperature freezing cabinet 42 to facilitate siteinstallation and operation.

In the integrated system 41, the suction (inlet/intake/low pressure) endof the low-temperature compressor 52 is connected to the inlet end 102of the of the integrated unit 41 via the associated connecting pipes 44,the suction end of the medium-temperature compressor 53 is connected tothe inlet end 104 of the of the integrated unit 41 via the associatedconnecting pipes 44, thereby providing the respective connections of themedium-temperature compressor 53 and the low-temperature compressor 52to the evaporators 64 within the medium-temperature refrigeratingcabinet 43 and the low-temperature freezing cabinet 42. The exhaust(outlet/discharge/high pressure) end of the low-temperature compressor52 merges with the exhaust end of the medium-temperature compressor 53via the associated connecting pipes 44 and is connected to the inlet endof the condenser 54 via the associated connecting pipes 44. The outletend of the condenser 54 is connected to the inlet end of the reservoir55 via the connecting pipes 44.

The outlet end of the reservoir 55 is branched into three flowpaths/branches (formed by associated components including the connectingpipes 44) 71, 72, and 73. In the flow path 71, the outlet end of thereservoir 55 is directly connected to the inlet end of themedium-temperature refrigerating cabinet 43 via the associatedconnecting pipes 44, thereby realizing connection of the outlet end ofthe reservoir 55 with the expansion valve 63 within themedium-temperature refrigerating cabinet 43. In the flow path 72, theoutlet end of the reservoir 55 is connected with the first inlet end ofthe intermediate heat exchanger 56, and is connected with the inlet endof the low-temperature freezing cabinet via the associated connectingpipes 44 at the first outlet end of the intermediate heat exchanger 56,thereby realizing the connection of the outlet end of the reservoir 55with the expansion valve 63 within the medium-temperature refrigeratingcabinet 43 via the first branch/segment 75 of the intermediate heatexchanger 56. In the flow path 73, the outlet end of the reservoir 55 isconnected to the inlet end of the expansion valve 57 via the associatedconnecting pipes 44, and is connected with the second inlet end of theintermediate heat exchanger 56 via the associated connecting pipes 44 atthe outlet end of the expansion valve 57. The flow path 73 continuesthrough the second branch/segment 76 of the intermediate heat exchanger56. The second branch/segment 76 is in heat exchange relation with thefirst branch/segment 75. The second outlet end of the intermediate heatexchanger 56 is divided into two branches 431, 432. In the first branch431 the second outlet end of the intermediate heat exchanger 56 mergeswith the outlet end of the refrigerating cabinet 43 via the associatedconnecting pipes 44 and is directly connected to the suction end of themedium-temperature compressor 53. In the second branch 432, the secondoutlet end of the intermediate heat exchanger 56 is first connected tothe adjustment valve 58 via the associated connecting pipes 44, and thenmerges with the outlet end of the low-temperature freezing cabinet 42via the connecting pipes 44 for connecting to the suction end of thelow-temperature compressor 52.

When the system starts up, the low-temperature and low-pressure gaseousrefrigerant flowing out of the outlet ends of the medium-temperaturerefrigerating cabinet 43 and the low-temperature freezing cabinet 42flows into the medium-temperature compressor 53 and the low-temperaturecompressor 52 respectively, and they are compressed intohigh-temperature and high-pressure gas, and then merge together and flowtogether into the condenser 54. In the condenser 54, thehigh-temperature and high-pressure gaseous refrigerant becomeshigh-temperature and high-pressure liquid refrigerant after havingreleased heat to the ambient and flows into the reservoir 55. In theflow path 71 at the outlet end of the reservoir 55, the high-temperatureand high-pressure liquid refrigerant flows into the expansion valve 63within the medium-temperature refrigerating cabinet 43 via theassociated connecting pipes 44, changes into a low-temperature andlow-pressure liquid after throttling and pressure decreasing through theexpansion valve 63, flows through the coiled pipes in the evaporator 64within the medium-temperature refrigerating cabinet 43 and exchangesheat with the air on the surface of the coiled pipes to generatemedium-temperature cold air in order to transform the low-temperatureand low-pressure liquid refrigerant into low-temperature andlow-pressure gaseous refrigerant, and to flow back into themedium-temperature compressor 53, thus forming a circulating loop of themedium-temperature system. In the flow path 72, the high-temperature andhigh-pressure liquid refrigerant at the outlet end of the reservoir 55flows through the intermediate heat exchanger 56. In the flow path 73,the high-temperature and high-pressure liquid refrigerant at the outletend of the reservoir 55 is first changed into the low-temperature andlow-pressure liquid refrigerant via pressure-deceasing throttling viathe expansion valve, and then flows through the intermediate heatexchanger 56. The two refrigerant flows in the flow paths 72, 73 atdifferent temperatures exchange heat in the intermediate heat exchanger56. The high-temperature and high-pressure liquid refrigerant in theflow path 72 releases heat in the intermediate heat exchanger 56, makingthe high-temperature and high-pressure liquid refrigerant pre-cooledbefore flowing into the low-temperature freezing cabinet 42, therebyeffectively adjusting the subcooling of the low-temperature freezingsystem so as to improve refrigerating effects and performance of thelow-temperature freezing system. The pre-cooled refrigerant enters intothe expansion valve 63 of the low-temperature freezing cabinet 42 forthrottling to change into the low-temperature and low-pressure liquidrefrigerant, flows into the coiled pipes within the evaporator 64 andexchanges heat with the ambient air to supply low-temperature cold air.The heat-absorbed gaseous refrigerant flows back into thelow-temperature compressor 52 to form a circulating loop of thelow-temperature freezing system. The low-temperature and low-pressureliquid refrigerant in the flow path 73 absorbs heat within theintermediate heat exchanger 56 to change into the low-temperature andlow-pressure gaseous refrigerant. There are two branches 431 and 432 forthe refrigerant flowing out of the intermediate heat exchanger 56. Inthe first branch 431, the low-temperature and low-pressure gaseousrefrigerant merges directly with the low-temperature and low-pressuregaseous refrigerant flowing out of the medium-temperature refrigeratingcabinet 43 and flows into the medium-temperature compressor 53. In thesecond branch 432, the low-temperature and low-pressure gaseousrefrigerant first flows through the adjustment valve 58, merges with thelow-temperature and low-pressure gaseous refrigerant flowing out of thelow-temperature freezing cabinet 42 and then flows into thelow-temperature compressor 52, thereby effectively adjusting the suctiontemperature of the low-temperature compressor via the adjustment valve58 and protecting the low-temperature compressor 42. Control may beautomatic via a controller (e.g., an electronic control system such as amicrocontroller) responsive to sensor (not shown) input and any user-setor user-input parameters or commands

It is easily understood that the medium- and low-temperature integratedrefrigerating/freezing system of the present invention comprises theintegrated unit 41, the (group of) medium-temperature refrigeratingcabinet(s) 42, the (group of) low-temperature freezing cabinet(s) 43 andthe connecting pipes 44. In the integrated unit 41 the medium- andlow-temperature freezing systems share one condenser 54 and thereservoir 55; the expansion valve 57, the intermediate heat exchanger 56and the corresponding connecting pipes 44 form the subcooling adjustingmechanism of the low-temperature freezing system for adjustingsubcooling of the low-temperature freezing system and improving theoverall performance and the stability of the low-temperature freezingsystem; the expansion valve 57, the intermediate heat exchanger 56, theadjustment valve 58 and the corresponding connecting pipes 44 furtherform an suction temperature adjusting mechanism for the low-temperaturefreezing system for lowering the suction temperature of thelow-temperature freezing system in order to better protect thelow-temperature compressor 52.

By using such a medium- and low-temperature integratedrefrigerating/freezing system, it can effectively reduce theinstallation space for the system, and the integrated unit can bedirectly installed outdoors, such as on a roof. The costs of the wholesystem are significantly less than that of two independentmedium-temperature and low-temperature systems. The optimization of thepipelines within the integrated unit and the plug-and-play connectionbetween the integrated unit and the medium-temperature andlow-temperature freezing cabinets facilitate site installation and dailymaintenance of the devices. The performance of the whole system, inparticular of the low-temperature system, has very high stability.

Although an embodiment is described above in detail, such description isnot intended for limiting the scope of the present disclosure. It willbe understood that various modifications may be made without departingfrom the spirit and scope of the disclosure. For example, whenimplemented in the reengineering of an existing container configuration,details of the existing configuration may influence or dictate detailsof any particular implementation. Accordingly, other embodiments arewithin the scope of the following claims.

1. A medium- and low-temperature integrated refrigerating/freezingsystem (40) for providing refrigerating medium temperature for foodstorage, etc. and freezing-low temperature for cold drink storage, etc.,which comprising an integrated unit (41), a (group of)medium-temperature refrigerating cabinet(s) (43), a (group of)low-temperature freezing cabinet(s) (42) and corresponding connectingpipes (44), wherein said integrated unit comprises: a common condenser(54) for condensing high-temperature and high-pressure gaseousrefrigerant in the medium-temperature refrigerating system and thelow-temperature freezing system; a common reservoir (55) for storing thehigh-temperature and high-pressure liquid refrigerant in themedium-temperature refrigerating system and the low-temperature freezingsystem; a subcooling adjusting mechanism (56, 57) for adjusting thesubcooling in the low-temperature freezing system; and a suctiontemperature adjusting mechanism (431, 432, 58) for adjusting the suctiontemperature of the low-temperature freezing system.
 2. The medium- andlow-temperature integrated refrigerating/freezing system as claimed inclaim 1, wherein said integrated unit further comprises a (group of)medium-temperature compressor(s) (53) and a (group of) low-temperaturecompressor(s) (52).
 3. The medium- and low-temperature integratedrefrigerating/freezing system as claimed in claim 2, wherein saidmedium-temperature refrigerating cabinet(s) and said low-temperaturefreezing cabinet(s) comprise respectively an evaporator (64), anexpansion valve (63) and a product cabinet (61) for food placement. 4.The medium- and low-temperature integrated refrigerating/freezing systemas claimed in claim 3, wherein the suction end(s) of saidmedium-temperature compressor(s) and low-temperature compressor(s) arerespectively connected to the evaporators of the medium-temperaturerefrigerating cabinet(s) and the low-temperature freezing cabinet(s),and the exhaust ends thereof are jointly connected to the inlet end ofsaid common condenser.
 5. The medium- and low-temperature integratedrefrigerating/freezing system as claimed in claim 4, wherein the outletend of the common condenser (54) is connected to the inlet end of thereservoir (55).
 6. The medium- and low-temperature integratedrefrigerating/freezing system as claimed in claim 5, wherein anexpansion valve (57), an intermediate heat exchanger (56) and saidcorresponding connecting pipes in said integrated unit form saidsubcooling adjusting mechanism.
 7. The medium- and low-temperatureintegrated refrigerating/freezing system as claimed in claim 6, whereina first inlet end of the intermediate heat exchanger of said subcoolingadjusting mechanism is directly connected to said reservoir, and asecond inlet end is connected to said reservoir via said expansionvalve.
 8. The medium- and low-temperature integratedrefrigerating/freezing system as claimed in claim 7, wherein a firstoutlet end of said intermediate heat exchanger is connected to an inletend of said low-temperature freezing cabinet.
 9. The medium- andlow-temperature integrated refrigerating/freezing system as claimed inclaim 8, wherein said suction temperature adjusting mechanism comprisesa first branch (431) connecting a second outlet end of said intermediateheat exchanger (56) with the suction end of said medium-temperaturecompressor (53), and a second branch (432) connecting the second outletend of said intermediate heat exchanger with the suction end of saidlow-temperature (52) compressor, wherein said second branch contains anadjustment valve (58).
 10. The medium- and low-temperature integratedrefrigerating/freezing system as claimed in claim 1, wherein theintegrated unit is connected to said medium-temperature refrigeratingcabinet and said low-temperature freezing cabinet in a plug-and-playmanner.
 11. A refrigerating system (40) comprising: at least onemedium-temperature refrigerating device (43) comprising at least onemedium-temperature evaporator; at least one low-temperature freezingdevice (42) comprising at least one low-temperature evaporator; and anintegrated unit (41) comprising: at least one medium-temperaturecompressor (53) connected to said medium-temperature evaporator; atleast one low-temperature compressor (52) connected to saidlow-temperature evaporator; a condenser (54) connected to the exhaustends of said at least one medium-temperature compressor and the at leastone low-temperature compressor, for condensing the high-temperature andhigh-pressure gaseous refrigerant exhausted from the exhaust ends ofsaid at least one medium-temperature compressor and the at least onelow-temperature compressor; a reservoir (55) connected to said condenserfor storing the high-temperature and high-pressure liquid refrigerantexhausted from the condenser; a subcooling adjusting mechanism (56, 57)connected with said reservoir and to said low-temperature evaporator foradjusting the subcooling of a low-temperature freezing circulationsystem; a suction temperature adjusting mechanism (431, 432, 58)connected with said reservoir and respectively to said low-temperaturecompressor and said medium-temperature compressor, for adjusting thesuction temperature of the low-temperature freezing circulation system;and a medium-temperature connecting pipeline (71) connected to saidreservoir and the medium-temperature evaporator.
 12. The refrigeratingsystem as claimed in claim 11, wherein said subcooling adjustingmechanism comprises an intermediate heat exchanger (56) connected tosaid low-temperature evaporator, a first inlet end thereof is directlyconnected to said reservoir, and a second inlet end thereof is connectedto said reservoir via an expansion valve.
 13. The refrigerating systemas claimed in claim 12, wherein a first outlet end of said intermediateheat exchanger is connected to the low-temperature evaporator of saidlow-temperature freezing device.
 14. The refrigerating system as claimedin claim 13, wherein said suction temperature adjusting mechanismcomprises a first branch connecting the second outlet end of saidintermediate heat exchanger with the suction end of saidmedium-temperature compressor, and a second branch connecting the secondoutlet end of said intermediate heat exchanger with the suction end ofsaid low-temperature compressor, wherein said second branch contains anadjustment valve.
 15. A refrigeration system (40) comprising: a firstcompartment (42); a second compartment (43); at least one compressor(52, 53) for compressing refrigerant; a condenser (54) for condensingcompressed refrigerant from the at least one compressor; a reservoir forstoring condensed refrigerant; a first expansion device and a firstevaporator in a flow path (72) associated with the first compartment forexpanding refrigerant and cooling the first compartment; and a secondexpansion device and second evaporator in a flow path (71) associatedwith the second compartment for expanding the condensed refrigerant andcooling the second compartment, further characterized by: means (56, 57,58, 431, 432) for adjusting a degree of overcooling and adjusting asuction temperature of refrigerant associated with the firstcompartment.
 16. The system of claim 15 wherein: the condenser (54) andthe reservoir (55) are common to the flow path (72) associated with thefirst compartment and the flow path (71) associated with the secondcompartment.
 17. A method for operating the system of claim 15,comprising: under automated control, using said means for adjusting toadjust the degree of subcooling and the suction temperature ofrefrigerant associated with the first compartment.